function Drag() {
	//初始化
	this.initialize.apply(this, arguments)
}
Drag.prototype = {
	//初始化
	initialize : function (drag, options)  {
		this.drag = this.$(drag);
		this._x = this._y = 0;
		this._moveDrag = this.bind(this, this.moveDrag);
		this._stopDrag = this.bind(this, this.stopDrag);
		this.setOptions(options);
		this.handle = this.$(this.options.handle);
		this.maxContainer = this.$(this.options.maxContainer);
		this.maxTop = Math.max(this.maxContainer.clientHeight, this.maxContainer.scrollHeight) - this.drag.offsetHeight;
		this.maxLeft = Math.max(this.maxContainer.clientWidth, this.maxContainer.scrollWidth) - this.drag.offsetWidth;
		this.limit = this.options.limit;
		this.lockX = this.options.lockX;
		this.lockY = this.options.lockY;
		this.lock = this.options.lock;
		this.onStart = this.options.onStart;
		this.onMove = this.options.onMove;
		this.onStop = this.options.onStop;
		this.handle.style.cursor = "move";
		this.changeLayout();
		this.addHandler(this.handle, "mousedown", this.bind(this, this.startDrag))
	},
	changeLayout : function ()  {
		this.drag.style.top = this.drag.offsetTop + "px";
		this.drag.style.left = this.drag.offsetLeft + "px";
		this.drag.style.position = "absolute";
		this.drag.style.margin = "0"
	},
	startDrag : function (event)  {
		event = event || window.event;
		this._x = event.clientX - this.drag.offsetLeft;
		this._y = event.clientY - this.drag.offsetTop;
		this.addHandler(document, "mousemove", this._moveDrag);
		this.addHandler(document, "mouseup", this._stopDrag);
		event.preventDefault && event.preventDefault();
		this.handle.setCapture && this.handle.setCapture();
		this.onStart()
	},
	moveDrag : function (event)  {
		event = event || window.event;
		var iTop = event.clientY - this._y;
		var iLeft = event.clientX - this._x;
		if (this.lock)
			return;
		this.limit || iTop >= 0 || (iTop = 0);
		this.limit || iTop < this.maxContainer.clientHeight - 5 || (iTop = this.maxContainer.clientHeight - 5);
		this.limit || iLeft < this.maxContainer.clientWidth - 7 || (iLeft = this.maxContainer.clientWidth - 7);
		this.limit && (iTop < 0 && (iTop = 0), iLeft < 0 && (iLeft = 0), iTop > this.maxTop && (iTop = this.maxTop), iLeft > this.maxLeft && (iLeft = this.maxLeft));
		this.lockY || (this.drag.style.top = iTop + "px");
		this.lockX || (this.drag.style.left = iLeft + "px");
		event.preventDefault && event.preventDefault();
		this.onMove()
	},
	stopDrag : function ()  {
		this.removeHandler(document, "mousemove", this._moveDrag);
		this.removeHandler(document, "mouseup", this._stopDrag);
		this.handle.releaseCapture && this.handle.releaseCapture();
		this.onStop()
	},
	//参数设置
	setOptions : function (options)  {
		this.options =  {
			handle:  this.drag, //事件对象
			limit:  true, //锁定范围
			lock:  false, //锁定位置
			lockX:  false, //锁定水平位置
			lockY:  false, //锁定垂直位置
			maxContainer: document.documentElement || document.body, //指定限制容器
			onStart: function () {}, //开始时回调函数
			onMove:  function () {}, //拖拽时回调函数
			onStop:  function () {} //停止时回调函数
		};
		for (var p in options)
			this.options[p] = options[p]
	},
	//获取id
	$ : function (id)  {
		return typeof id === "string" ? document.getElementById(id) : id
	},
	//添加绑定事件
	addHandler : function (oElement, sEventType, fnHandler)  {
		return oElement.addEventListener ? oElement.addEventListener(sEventType, fnHandler, false) : oElement.attachEvent("on" + sEventType, fnHandler)  
	},
	//删除绑定事件
	removeHandler : function (oElement, sEventType, fnHandler)  {
		return oElement.removeEventListener ? oElement.removeEventListener(sEventType, fnHandler, false) : oElement.detachEvent("on" + sEventType, fnHandler)  
	},
	//绑定事件到对象
	bind : function (object, fnHandler)  {
		return function ()  {
			return fnHandler.apply(object, arguments)
		}
	}
};